1997 Chevy Cavalier instrument cluster

hey, I have a problem with my 97 cavalier, recently, my speedometer quit working, it works when it wants and fluctuates really bad sometimes, the problem is I took the needles off when I shouldnt have, so now I think its out of calibration or something, also would it have something to do with the radio wires, I recently put in a not factory radio and cut the main harness, I didnt buy the new harness, so my other question would be does the radio wires have anything to do with the speedometer cluster? Also if I get a new cluster how do I get my milage right again? Please respond asap thanks for your time and help